The present invention relates to photodecomposing organosilicon compounds and photopolymerizable epoxy resin compositions containing the organosilicon compounds.
Recently, photosetting processes for curing resins are attracting much attention from the viewpoint of energy saving and improvement on working efficiency. Among the photosetting processes, in particular, a curing process of photopolymerizing epoxy resin in the presence of a catalyst composed of a photodecomposing organosilicon compound and a metal complex has wide application and has the following advantages over other processes:
(a) Satisfactory photosetting can be performed by photopolymerization and the cured products obtained by this process have excellent electric characteristics as reported in "Nippon Kagaku Kaishi" 1985, (3), p.328-333.
(b) This process enables the production of reliable materials for use in optical information recording medium in a short curing time with high productivity.
(c) This process provides an adhesive agent suitable, for example, for devices using liquid crystals.
Varieties of photopolymerizable epoxy resin compositions have been proposed. For example, Japanese Laid-Open Patent Application No. 61-221 discloses a composition in which an organosilicon compound having the following general formula (I) and an aluminum compound are blended together with epoxy resin. The thus blended epoxy resin is evaluated as having particularly high photo-setting speed ("Nippon Kagaku Kaishi" 1985, (3), p.328-333). ##STR2## wherein R.sup.1 represents a lower alkyl group, a lower unsaturated alkyl group or an aromatic group; R.sup.2, R.sup.3, R.sup.4 and R.sup.5 each represent hydrogen, halogen, or an organic group such as an alkyl group, an aryl group, a nitro group, a cyano group, and an alkoxyl group, which may be the same or different; m is an integer of 0 to 2; and n is an integer of 1 to 3, provided that m+n is not more than 3 (m+n.ltoreq.3).
Japanese Laid-Open Patent Application No. 58-174389 describes in detail the photodecomposing organosilicon compounds having the above-mentioned structure and a method of producing the same.
The photopolymerizable epoxy resin compositions prepared by the above-mentioned conventional methods are excellent in electric characteristics and resistant to corrosion, but have the shortcomings that the photo-setting speed is low at low temperatures and accordingly the productivity thereof is too low for actual production.
In the case of the above conventional photopolymerizable epoxy resin compositions, their photo-setting speed can be increased by raising the photo-setting temperature. However, when the photo-setting temperature is raised too much, the temperature of other materials which are in contact with the epoxy resin compositions is also raised, with the result that physical changes may occur in some of the materials, which may also cause the production of improper products. In addition, these compositions have another significant shortcoming that the pot-life is so short that workability is unsatisfactory.